The present invention relates to bookbinding machines in general, and more particularly to improvements in apparatus for gathering folded sheets or groups of folded sheets in bookbinding machines. Still more particularly, the invention relates to improvements in those units of sheet gathering apparatus which effect the delivery of folded sheets or groups of folded sheets from discrete magazines (e.g., pockets or bins) onto an endless conveyor which transports piles of gathered sheets to one or more further processing stations.
Presently known gathering apparatus comprise an endless conveyor which has an upper reach advancing along a substantially horizontal path past several delivery stations at each of which the upper reach receives a different folded sheet or group of folded sheets. Identical folded sheets or groups of folded sheets are stored in the aforementioned magazines, and each delivery station accommodates a withdrawing device which removes the lowermost sheet or lowermost group of sheets from the stack in the respective magazine and means for spreading or opening the leaves of the sheet or group of sheets prior to actual descent of sheets or groups of sheets onto the upper reach of the conveyor. As a rule, the spreading means deposit folded but opened sheets or groups of folded but opened sheets onto blade-like intercepting members, and the conveyor has entraining elements or pushers which transfer the sheets from the intercepting members onto the upper reach of the conveyor.
A drawback of the just described gathering apparatus is that folded sheets or groups of folded sheets are not guided during movement from the range of spreading means onto the corresponding intercepting members. This presents problems when the conveyor is driven at a relatively high speed because the position and/or orientation of sheets can deviate from an optimum position and/or orientation at the time they are engaged and entrained by the oncoming pushers. For example, the descent of sheets can be too slow so that they are not entrained by the oncoming pushers. Moreover, the sheets are likely to change their position on the upper reach if the conveyor is driven at a relatively high speed.